Most modern rifle scopes include a reticle that is internally adjustable by the user, using scope turrets, in both vertical and horizontal planes to a “zero” point at a known distance from a target. A windage turret controls internal adjustment of the reticle laterally (i.e., left and right) to account for changes in windage, and an elevation turret controls internal adjustment of the reticle vertically to account for changes in target distance (also referred to as “elevation”).
A rifle scope is typically mounted to a rifle using two or more mounting rings that clamp around the tube of the scope and hold the scope at a fixed distance above the barrel bore of the rifle. Conventional scope mounting rings are available in a variety of fixed heights to accommodate a number of factors, including diameter of the scope's objective lens, profile of the barrel, height of any mounting device or base used between the scope rings and the rifle, and the comb height of the stock where the user rests (“welds”) his cheek to align his eye with the scope for proper sighting. While scope mounting rings are available in a wide variety of heights, the height is fixed and the user generally must select only one height dimension or purchase multiple sets of scope mounting rings to accommodate different installations or to allow the scope mounted on different rifles.
Internal adjustment of the reticle is typically adequate to allow a “zero” adjustment at short to moderate ranges. However, at longer ranges (e.g., beyond one thousand yards), this internal adjustment may be inadequate, especially to compensate for lateral misalignment between the barrel bore and axis of the scope or mounting rings. Further, an initial “zero” of a scope mounted to a rifle is generally set at either an indoor range or other place where environmental conditions are controlled and there is no cross wind. In an ordinary scope mounting system, lateral angular adjustment is done by way of the internal adjustment of the reticle using the scope's adjustment turrets. In some cases, especially where the longitudinal orientation of the mounting base is not perfectly parallel to the bore axis of the rifle barrel, a significant portion of the lateral “windage” adjustment is used to set the “zero” position of the scope, thus leaving little adjustment range available for fine-tuning in the field.
Previous attempts to provide adjustable scope mounting rings have proved inadequate in various ways, including lacking sufficient strength and rigidity to maintain precise alignment under the heavy recoil impact of larger caliber rifles commonly used to shoot at long ranges. Accordingly, there is a need for improvements to known scope mounting devices that address these and other shortcomings.